A wide variety of human-implantable medical devices for automatically performing various therapeutic and diagnostic functions are known and commercially available. Such devices include pacemakers, cardioverters, defibrillators, and cardiac monitors, as well as neural simulators, drug-administering devices, and the like. The Medtronic, Inc. Model 7217 PCD is one example of an implantable medical device. This device is capable of pacing, cardioverting, and defibrillating a patient's heart through delivery of electrical stimulating pulses. In the case of defibrillation, those stimulating pulses can be very strong, on the order of 35 Joules or 750-volts or so.
Such implantable devices are often powered by an internal battery which permits the device to function continuously over a long period of time, in some cases up to a decade or more. When a patient with an implanted device dies, the device will often be explanted by a pathologist or an undertaker. This is especially important in instances where the body is to be cremated since the device could explode due to extreme heat
With more and more patients having devices implanted, the risk that a person will receive a shock during explant manipulations, for example from an implanted defibrillator, is becoming of increasing concern. A shock during explant may arise because the sensing electrodes used to detect arrhythmic events may receive spurious signals caused by the explant manipulations. These spurious signals could cause the device to "believe" an arrhythmic event is occurring and initiate a therapy, i.e. deliver electric shocks. Usually these shocks are delivered through the electrodes. The potential for injurious shock during explant manipulation may be heightened, however, in situations involving so-called "active canister" devices. Those devices deliver electric shocks through both an electrode as well as the device canister itself. Thus even if the explantor is holding only one electrode, while also holding the device itself, electrical shocks may be delivered. One example of such an active canister implantable defibrillator is the Medtronic, Inc. Model 7219 C. This device is presently undergoing clinical trials in the United States.
At present, one manner in which the potential for injury during explant of implantable devices is addressed is through physician's manuals. These manuals instruct that the devices be programmed to an inactive state upon the death of the patient. The explantor, however, may not have the appropriate programming apparatus at their disposal. Moreover, in many cases the explantor will never have seen the physician's manual for the device. Indeed they may not even become aware a device has been implanted until after the autopsy or embalming process has begun.
In order to reduce the potential that electrical stimulating pulses would occur during explant, it would be desirable to provide a mechanism whereby operation of the device is automatically inhibited or deactivated upon the death of the patient.